Elevator systems include a variety of components for controlling movement of the elevator car. For example, an elevator brake is responsible for decelerating a moving elevator car and holding a parked car at the proper landing. Typical elevator brakes are applied by spring force and lifted or released by electric actuation. Power is required to the brake for lifting the brake so that the elevator car can move. In the event of power loss, for example, the spring force applies the brake to prevent undesired movement of the elevator car.
An elevator safety chain is associated with the components that supply power to the brake. The safety chain provides an indication of the status of the elevator car doors or any of the doors along the hoistway. When the safety chain indicates that at least one door is open, for example, the elevator car should not be allowed to move.
Allowing the safety chain to control whether power is supplied to the elevator brake has typically been accomplished using high cost relays. Elevator codes require confirming proper operation of those relays. Therefore, relatively expensive, force guided relays are typically utilized for that purpose. The force guided relays are expensive and require significant space on drive circuit boards. Force guided relays are useful because they allow for monitoring relay actuation in a fail safe manner. They include two contacts, one of which is normally closed and the other of which is normally open. One of the contacts allows for the state of the other to be monitored, which fulfills the need for monitoring actuation of the relays.
Elevator system designers are always striving to reduce cost and space requirements. Force guided relays interfere with accomplishing both of those goals because they are relatively expensive and require a relatively large amount of space on a circuit board, for example.